Expandable fusion device for positioning between adjacent vertebral bodies

ABSTRACT

In some embodiments, system and/or method may include an intervertebral implant for a human spine including an upper body, a lower body, first and second expansion members, and an expansion mechanism. A superior surface of the upper body may function to engage a first vertebra of the human spine. An inferior surface of the lower body may function to engage a second vertebra of the human spine. The first expansion member may include at least a first angled portion positionable, during use, between the upper body and the lower body. The second expansion member may include at least a second angled portion positionable, during use, between the upper body and the lower body. An expansion mechanism may convey, during use, the first and second angled portions in opposing directions increasing a separation distance between the upper body and the lower body.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent Application No. 61/766,982 entitled “EXPANDABLE FUSION DEVICE FOR POSITIONING BETWEEN ADJACENT VERTEBRAL BODIES” filed on Feb. 20, 2013, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to spinal implant devices and methods for promoting fusion between adjacent vertebral bodies, and more particularly to expandable fusion devices that can be inserted between adjacent vertebral bodies to facilitate the fusion thereof.

2. Description of the Relevant Art

The human spine is a complex mechanical structure, composed of alternating bony vertebrae and fibrocartilaginous discs that are connected by strong ligaments and supported by musculature, that extends from the skull to the pelvis and provides axial support for the body.

The vertebrae generally comprise a vertebral foramen bounded by the anterior vertebral body and the neural arch. The vertebral body comprises two end plates (i.e., superior and inferior) made of thin cartilage overlying a thin layer of hard cortical bone that attaches to the spongy, cancellous interior bone of the vertebral body. The neural arch consists of two pedicles and two lamina that are united posteriorly. The spinous and transverse processes protrude from the neural arch. The superior and inferior articular facets lie at the root of the transverse processes.

The intervertebral discs primarily serve as a mechanical cushion between adjacent vertebral segments of the spinal column and generally comprise two basic components: the annulus fibrosis and the nucleus pulposus. The annulus fibrosis forms the outer perimeter of the disc and is a tough ring that binds adjacent vertebrae together. The nucleus pulposus fills the interior of the disc and carries load.

The spine as a whole is a highly flexible structure capable of a high degree of curvature and twist in nearly every direction. However, genetic or developmental irregularities, trauma, chronic stress, and degenerative wear can result in spinal pathologies for which surgical intervention may be necessary.

It is common practice to remove a spinal disc in cases of spinal disc deterioration, disease or spinal injury. More particularly, the discs sometimes become diseased or damaged such that the height of the disc is reduced, which causes the annulus to buckle in areas where the laminated plies are loosely bonded. As the overlapping laminated plies of the annulus begin to buckle and separate, circumferential and/or radial annular tears may occur, allowing nucleus material to escape or form a bulge in the annulus. Such disruption to the natural intervertebral separation and the resulting herniation produces pain, which can be alleviated by removal of the disc and restoration of the natural separation distance. In cases of chronic back or leg pain resulting from a degenerated or herniated disc, removal of the disc can become the desired course of treatment.

In some cases it is desired to fuse the adjacent vertebrae together after removal of the disc. Such a procedure is sometimes referred to as “intervertebral fusion” or “interbody fusion”.

Many techniques and instruments have been devised to perform intervertebral fusion. There is common agreement that the strongest intervertebral fusion is interbody fusion between the lumbar bodies, which may be augmented by a posterior or facet fusion. In cases of intervertebral fusion, either structural bone, or a rigid interbody fusion “cage” typically filled with morselized bone, is placed centrally within the space where the spinal disc once resided. Multiple bony grafts or cages may be used within that space. Furthermore, multiple surgical approaches may be utilized, including anterior, posterior, or lateral surgical approaches.

Such practices are characterized by certain disadvantages, including the need to distract the disc space in order to implant the fusion device and thereby restore the diseased disc space to its normal or healthy height. However, it can be difficult to distract the adjacent vertebral bodies sufficiently to easily insert the fusion device between adjacent vertebral bodies. As a result, it is often necessary to drive the fusion device into the space between the vertebral bodies using impaction with a mallet and the application of significant force. The use of such impaction and force increases the risk of damage to local soft tissue such as blood vessels and the surrounding nerves, and can lead to suboptimal placement and/or failure of the insertion instrumentation. Furthermore, the use of such impaction and force can damage or compromise the vertebral endplates, resulting in eventual failure and subsidence of the fusion device into the vertebral bodies and hence loss of disc height.

Therefore, there is a need for a fusion device that can be placed between adjacent vertebral bodies at minimal height and, thereafter, be variably adjusted with minimal force application to the preferred height for an individual patient. Furthermore, it is desirable that the expandable fusion device be maintained in a closed (i.e., unexpanded) position during insertion and handling, and that it be rigidly attachable to a holder so as to facilitate maximum control by the surgeon during insertion and deployment.

SUMMARY

Accordingly, there is now provided an expandable fusion device that can be placed between adjacent vertebral bodies at minimal height and, thereafter, be variably adjusted with minimal force application to the preferred height for an individual patient. In one embodiment, an expandable PLIF (Posterior Lumbar Interbody Fusion) device or an expandable TLIF (Transforaminal Lumbar Interbody Fusion) device, is disclosed. The expandable fusion device generally includes: a cage, superior and lower bodys, and an expansion mechanism with opposing proximal and second expansion members. The application of torque to the expansion mechanism in one direction causes the proximal and second expansion members to separate, whereby to move the superior and lower bodies away from one another and hence increase the height of expandable fusion device 5. The application of torque to the expansion mechanism in the opposite direction causes the proximal and second expansion members to approach one another, whereby to move the superior and lower bodys toward one another and hence decrease the height of the expandable fusion device.

Further embodiments may include: (i) angled or lordotic superior and lower bodys to match the angle of the disc space; (ii) mismatched proximal and second expansion members, such that the anterior portion of the expandable fusion device opens more than the posterior portion of the expandable fusion device, thereby resulting in a fusion device that increases in both height and lordosis; (iii) dual or multiple expansion mechanisms for anterior spinal approaches; (iv) a curved or flexible holder for the expandable fusion device for oblique access approaches; and (v) additional angled components (i.e., intermediate the aforementioned proximal and second expansion members) for longer expandable fusion devices.

In some embodiments, system and/or method may include an intervertebral implant for a human spine including an upper body, a lower body, first and second expansion members, and an expansion mechanism. The upper body may include an inferior surface and a superior surface. The superior surface of the upper body may function to engage a first vertebra of the human spine. The lower body may include a superior surface and an inferior surface. The inferior surface of the lower body may function to engage a second vertebra of the human spine.

The first expansion member may include at least a first angled portion. The first angled portion may be positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body. At least the first angled portion may be oriented towards a first end of the intervertebral implant. The second expansion member may include at least a second angled portion positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body. At least the second angled portion may be oriented towards a second end of the intervertebral implant. At least the second angled portion may be oriented in an opposing direction relative to at least the first angled portion. An expansion mechanism may convey, during use, the first and second angled portions in opposing directions increasing a separation distance between the upper body and the lower body. The first and/or second angled portion may include a wedge-shaped portion.

In some embodiments, the expansion mechanism may include a threaded elongated member. The threaded elongated member may include a proximally threaded portion. The first expansion member may include a threaded opening which the threaded portion of the elongated member engages, during use.

In some embodiments, a distal end of the elongated member engages, during use, a proximal end of the second expansion member. The distal end may engage a recess in the second expansion member and rotates freely within it.

In some embodiments, the expansion mechanism may include a first elongated member and a second elongated member. The first elongated member may include a proximally threaded portion. The first expansion member may include a threaded opening which the threaded portion of the first elongated member engages, during use. The second elongated member may be positionable, during use, in an opening in the second expansion member. A distal end of the first elongated member may engage, during use, a proximal end of the second elongated member. In some embodiments, a distal end of the first elongated member may engage, during use, a proximal end of the second elongated member such that the distal end of the first elongated member is positioned in the opening in the second expansion member.

In some embodiments, the expansion member may include a locking member. The locking member may be positionable in the second expansion member such that the distal end of the first elongated member is inhibited, during use, from removal from the opening in the second expansion member.

In some embodiments, the intervertebral implant may include a cage. The cage may form a perimeter around the intervertebral implant in which at least portions of the upper body, the lower body, the first expansion member, the second expansion member, and the expansion mechanism are positioned, during use, in the cage. The cage may include one or more openings along the perimeter to allow graft material to be positioned during use.

In some embodiments, a lateral cross section of a perimeter of the intervertebral implant may include a curved shape such that at least a first portion of the perimeter is substantially convex and at least a second portion of the perimeter is substantially concave, wherein the second portion is substantially opposite the first portion.

In some embodiments, the upper body and/or the lower body may include an opening wherein graft material is positionable during use. The upper body and/or the lower body may include an opening which increases in size as the first and second angled portions are conveyed in opposing directions.

In some embodiments, the superior surface of the upper body and/or the inferior surface of the lower body may include protrusions (e.g., teeth). The protrusions may promote, during use, retention of the implant between the first vertebra and the second vertebra after insertion.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description of the preferred embodiments and upon reference to the accompanying drawings.

FIG. 1 depicts a schematic side view showing an expandable fusion device formed in accordance with the present invention, with the expandable fusion device being disposed between adjacent vertebral bodies.

FIG. 2 depicts a schematic exploded view of an expandable fusion device.

FIG. 3 depicts a schematic front perspective view of an expandable fusion device, with the expandable fusion device being shown in an unexpanded position.

FIG. 4 depicts a schematic front perspective view of an expandable fusion device, with the expandable fusion device being shown in an expanded position.

FIG. 5 depicts a schematic rear perspective view of an expandable fusion device, with the expandable fusion device being shown in an unexpanded position.

FIG. 6 depicts a schematic rear perspective view of an expandable fusion device, with the expandable fusion device being shown in an expanded position.

FIG. 7 is a schematic side view of an expandable fusion device, with the expandable fusion device being shown in an unexpanded position.

FIG. 8 depicts a schematic side view of an expandable fusion device, with the expandable fusion device being shown in an expanded position.

FIG. 9 depicts a schematic top view of an expandable fusion device.

FIG. 10 depicts a schematic side cross-sectional view of an expandable fusion device, with the expandable fusion device being shown in an unexpanded position.

FIG. 11 depicts a schematic side cross-sectional view of an expandable fusion device, with the expandable fusion device being shown in an expanded position.

FIG. 12 depicts a schematic perspective cross-sectional view of an expandable fusion device, with the expandable fusion device being shown in an unexpanded condition.

FIG. 13 depicts a schematic perspective view of a lower body.

FIG. 14 depicts a schematic perspective cross-sectional view of a lower body.

FIG. 15 depicts a schematic perspective cross-sectional view of an upper body.

FIG. 16 depicts a schematic right side perspective view of the proximal and second expansion members.

FIG. 17 depicts a schematic left side perspective view of the proximal and second expansion members.

FIG. 18 depicts a schematic view showing insertion instruments for use with an expandable fusion device.

FIG. 19 depicts a schematic transparent side view of an expandable fusion device.

FIG. 20 depicts a schematic exploded view of an expandable fusion device.

FIG. 21 depicts a schematic cross-sectional view of a curved expandable fusion device in an unexpanded state.

FIG. 22 depicts a schematic cross-sectional view of a curved expandable fusion device in an expanded state.

FIG. 23 depicts a schematic view of a curved expandable fusion device as the device is being inserted between two adjacent vertebrae.

FIG. 24 depicts a schematic view showing insertion instruments for use with an expandable fusion device.

FIG. 25 depicts a schematic view showing a distal end of an insertion instrument for use with an expandable fusion device.

FIG. 26 depicts a schematic view showing a proximal end of an insertion instrument for use with an expandable fusion device.

FIG. 27 depicts a schematic view of a disposable expandable fusion implant insertion device.

FIG. 28 depicts a schematic transparent view of a disposable expandable fusion implant insertion device.

FIG. 29 depicts a schematic perspective view of an expandable fusion implant in an expanded state wherein an upper body portion of the implant is depicted as transparent.

FIG. 30 depicts a schematic perspective view of an expandable fusion implant in an expanded state wherein an upper body portion of the implant is depicted as transparent.

FIG. 31 depicts a schematic perspective view of an expandable fusion implant in a contracted state.

FIG. 32 depicts a schematic perspective view of an expandable fusion implant in a contracted state coupled to an insertion instrument with portions of the insertion instruments depicted as transparent. An upper body of the implant is not depicted and a second expandable member is depicted as transparent.

FIG. 33 depicts a schematic view of an insertion instrument with an expandable fusion device.

FIG. 34 depicts a schematic view of a distal end of an insertion instrument with an expandable fusion device.

FIG. 35 depicts a schematic view of a distal end of an insertion instrument with an expandable fusion device with a portion of the insertion instrument removed for clarity.

FIG. 36 depicts a schematic view of a distal end of an insertion instrument with an expandable fusion device with a portion of the insertion instrument removed for clarity.

FIG. 37 depicts a schematic perspective view of an expandable fusion implant in a contracted state. At least an upper body and a cage of the implant is not depicted.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.

The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). The words “include,” “including,” and “includes” indicate open- ended relationships and therefore mean including, but not limited to. Similarly, the words “have,” “having,” and “has” also indicated open-ended relationships, and thus mean having, but not limited to. The terms “first,” “second,” “third,” and so forth as used herein are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.) unless such an ordering is otherwise explicitly indicated. For example, a “third die electrically connected to the module substrate” does not preclude scenarios in which a “fourth die electrically connected to the module substrate” is connected prior to the third die, unless otherwise specified. Similarly, a “second” feature does not require that a “first” feature be implemented prior to the “second” feature, unless otherwise specified.

Various components may be described as “configured to” perform a task or tasks. In such contexts, “configured to” is a broad recitation generally meaning “having structure that” performs the task or tasks during operation. As such, the component can be configured to perform the task even when the component is not currently performing that task (e.g., a set of electrical conductors may be configured to electrically connect a module to another module, even when the two modules are not connected). In some contexts, “configured to” may be a broad recitation of structure generally meaning “having circuitry that” performs the task or tasks during operation. As such, the component can be configured to perform the task even when the component is not currently on. In general, the circuitry that forms the structure corresponding to “configured to” may include hardware circuits.

Various components may be described as performing a task or tasks, for convenience in the description. Such descriptions should be interpreted as including the phrase “configured to.” Reciting a component that is configured to perform one or more tasks is expressly intended not to invoke 35 U.S.C. § 112, paragraph six, interpretation for that component.

The scope of the present disclosure includes any feature or combination of features disclosed herein (either explicitly or implicitly), or any generalization thereof, whether or not it mitigates any or all of the problems addressed herein. Accordingly, new claims may be formulated during prosecution of this application (or an application claiming priority thereto) to any such combination of features. In particular, with reference to the appended claims, features from dependent claims may be combined with those of the independent claims and features from respective independent claims may be combined in any appropriate manner and not merely in the specific combinations enumerated in the appended claims.

It is to be understood the present invention is not limited to particular devices or biological systems, which may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting. As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include singular and plural referents unless the content clearly dictates otherwise. Thus, for example, reference to “a linker” includes one or more linkers.

DETAILED DESCRIPTION Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

The term “connected” as used herein generally refers to pieces which may be joined or linked together.

The term “coupled” as used herein generally refers to pieces which may be used operatively with each other, or joined or linked together, with or without one or more intervening members.

The term “directly” as used herein generally refers to one structure in physical contact with another structure, or, when used in reference to a procedure, means that one process effects another process or structure without the involvement of an intermediate step or component.

Looking first at FIG. 1, there is shown an intervertebral implant 5 (e.g., expandable fusion device) formed in accordance with the present invention, with the intervertebral implant 5 being shown disposed between a superior vertebral body 10 and an inferior vertebral body 15. As will hereinafter be discussed in further detail, intervertebral implant 5 may be inserted between superior vertebral body 10 and inferior vertebral body 15 while the intervertebral implant is in a contracted condition (e.g., as depicted in FIGS. 3 and 5), and thereafter expanded (e.g., as depicted in FIGS. 4 and 6) as necessary so as to span and engage the endplate 20 of superior vertebral body 10 and the endplate 25 of inferior vertebral body 15, whereby to support superior vertebral body 10 and inferior vertebral body 15 relative to one another.

In some embodiments, (e.g., as depicted in FIG. 2) intervertebral implant 5 (e.g., as depicted in FIG. 2) generally includes a cage 30, an upper body 35, a lower body 40, an expansion mechanism 45, a first expansion member 50 (e.g., positioned proximally) and a second expansion member 55 (e.g., positioned distally). As will hereinafter be discussed, the application of torque to expansion mechanism 45 in one direction causes first expansion member 50 and second expansion member 55 to separate, whereby to move upper body 35 and lower body 40 away from one another and hence increase the height of intervertebral implant 5. The application of torque to expansion mechanism 45 in the opposite direction causes first expansion member 50 and second expansion member 55 to draw towards one another, whereby to move upper body 35 and lower body 40 toward one another and hence decrease the height of intervertebral implant 5. In some embodiments, the mechanism may be reversed with, for example, the expansion members moving towards one another during expansion (although the opening for biological material might be reduced in such an embodiment).

Designs which may be similar but with for example expansion members conveying in the same direction may have a mechanical disadvantage relative to the embodiments described herein wherein the expansion members are conveyed in opposing directions. Expansion members which are conveyed in opposing directions may require half of the input torque to move as opposed to expansion members which are conveyed in the same direction.

In some embodiments, a cage 30 includes a generally rectangular structure 60 having a hollow interior 65, a distal opening 70 and a proximal opening 75. Two seats 80 are formed in the opposing side surfaces of cage 30.

Upper body 35 generally includes a block 85 having an inferior recess 90, and a textured superior surface 95, and a pair of inclined camming surfaces 100, 105. Camming surfaces 100, 105 of upper body 35 may be inclined in opposite directions (e.g., as depicted in FIG. 15).

Lower body 40 generally includes a block 110 having a superior recess 115, a textured inferior surface 120 and a pair of inclined camming surfaces 125, 130. Camming surfaces 125, 130 of lower body 40 may be inclined in opposite directions (e.g., as depicted in FIGS. 13-14).

In some embodiments, the camming surface 100 of upper body 35 and the camming surfaces 130 of lower body 40 extend parallel to one another, and the camming surfaces 105 of upper body 35 and the camming surface 125 of lower body 40 extend parallel to one another.

Expansion mechanism 45 generally includes an elongated shaft 135 having an annular shoulder 140 formed intermediate its length. A groove 145 is formed distal to annular shoulder 140. Screw threads 147 are formed on the outer surface of elongated shaft 135 proximal to annular shoulder 140. A noncircular bore 150 opens on the proximal end of expansion mechanism 45 and extends distally thereof.

Superior and/or inferior surfaces of the implant (e.g., textured superior surface 95 and textured inferior surface 120) may include various features to facilitate engagement of the surfaces with endplates of adjacent vertebrae. In some embodiments, the implant may include a plurality of surface deformations positioned on the inferior surface and/or the superior surface. Surface deformations may include protrusions. For example (e.g., depicted in FIG. 7) superior surface of the implant 5 may include protrusions (e.g., teeth) 154 extending there from. During use, teeth 154 may extend/penetrate into adjacent boney structure of the upper and lower adjacent vertebrae. Such penetration may help to fix a position of the implant 5 relative to the vertebrae. Fixing or otherwise stabilizing the implant may reduce the likelihood of implant 5 being expelled from within the intervertebral space, and may promote bone attachment to and through implant 5. In some embodiments, various spray coatings may be applied to one or more exterior surfaces to, for example, enhance fixation with adjacent bone surfaces.

In some embodiments, protrusions 154 may include directional teeth that facilitate movement of the members in a first direction, but inhibit movement of the members in a second opposing direction. For example, in the illustrated embodiment, teeth 154 include a ramped leading surface 154 a and a substantially vertical trailing edge 154 b (e.g., depicted in FIGS. 7-8). Thus, forward advancement of the members may be facilitated as boney structure of the vertebrae slides over ramped leading surface 154 a of teeth 154 and backward advancement may be inhibited by substantially vertical trailing edge 154 b hooking into or otherwise engaging the boney structure of the vertebrae.

In some embodiments, one or more portions of the implant may include one or more markers. Markers may be used to assess a position of one or more portions of the implant during implantation in a subject. A portion of the implant may include none, one or multiple markers. Markers may provide radiographic opacity. Markers may be biocompatible. Markers may be of any size or shape. In some embodiments, a system may have multiple markers with different shapes in order to more easily identify different portions or directions of the system and/or an orientation of one or more portions of the implant. In some embodiments, one or more markers may be formed from gold or tantalum.

In some embodiments, the implant 5 may include an opening 152 a extending through the implant (e.g., depicted in FIGS. 9-12). The opening may hold biological material during use.

In some embodiments, opening 152 a may be filled with a substance/material to facilitate bone growth/fusion. Once implant 5 is implanted, the opening may facilitate a column of bone growth between the adjacent vertebrae through the opening 152 a. In some embodiments, an opening (e.g., opening 152 a) may function as a graft window containing bone chips and/or materials which facilitate tissue (e.g., bone) growth. The opening may increase in size as the first and second expansion members move away from each other as the implant is deployed.

In some embodiments, implant 5 may include one or more second openings 152 b (e.g., depicted in FIG. 20). The second openings may be positioned on either side of cage 30. The openings may facilitate insertion of biological material. After positioning an implant during use opening 152 a may be blocked by the vertebrae and therefore additional openings 152 b may facilitate in packing of biological material (e.g., bone graft). The openings may be initially at least partially blocked by the first and second expansion members and/or the upper and lower bodies, as the implant is expanded the second openings may open up.

In some embodiments, implant 5 may include a proximal opening 152 c (e.g., depicted in FIG. 29). A proximal opening may allow biological material to be positioned in the interior of the implant after the implant has been positioned. The proximal opening may facilitate insertion of biological material after insertion of the implant. In some embodiments, a proximal opening in the implant may necessitate positioning the expansion mechanism (e.g., elongated members 45 a-b as depicted in FIGS. 30-31) off center in order to allow for creating a large enough proximal opening. In some embodiments, the first expansion member 50 may be modified to allow biological material inserted through the proximal opening to pass beyond the first expansion member into the space between the first and the second expansion member 50, 55. The first expansion member may include an opening 156 and/or shaped to create an opening in combination with an interior surface of the cage 30 (e.g., as depicted in FIGS. 32 and 37).

In some embodiments, a distal end 235 of the elongated member (e.g., expansion mechanism 45 a) engages, during use, a proximal end of the second expansion member 55. In such an embodiment, the distal end of the elongated member abuts a proximal end of the second expansion member as opposed to extending through an opening in the second expansion member. The distal end may engage a recess 240 in the second expansion member 55 (e.g., as depicted in FIG. 19). A recess may include a shallow opening. The distal end may turn freely in the recess. The recess may assist in centering and/or positioning the distal end of the elongated member 45 such that the distal end is inhibited from misaligning and/or disengaging from the second expansion member. In some embodiments, the implant 5 may include a second elongated member 45 b. The second elongated member 45 b may be positioned in the second expansion member 55 and opening 70 such that the second elongated member keeps the second expansion member centered.

In some embodiments, the expansion mechanism may include a first elongated member 45 a and a second elongated member 45 b (e.g., as depicted in FIG. 20). The first elongated member 45 a may include a proximally threaded portion 147. The first expansion member 50 may include a threaded opening 180 which the threaded portion of the first elongated member engages, during use. The second elongated member 45 b may be positionable, during use, in an opening 210 in the second expansion member 55. A distal end 245 of the first elongated member 45 a may engage, during use, a proximal end 250 of the second elongated member 45 b. In some embodiments, a distal end of the first elongated member may engage, during use, a proximal end of the second elongated member such that the distal end of the first elongated member is positioned in the opening in the second expansion member. The distal end of the first elongated member may turn freely in the opening in the second expansion member. In some embodiments, the second elongated member may function to keep the second expansion member 55 central in the body of the implant. In some embodiments, the second elongated member may be essentially non-rotating relative to the first elongated member.

The result is that the separation between the expansion members is thus equal to just one pitch of the thread per rotation, or ½ pitch of movement relative to the endplate (upper & lower body) each. As such for a given torque one may provide approximately twice the lifting force as compared to dual expansion members moving in the same direction at 1 pitch per rotation. Embodiments discussed herein would have twice the separation force relative to a turnbuckle thread configured with opposing expansion members (or even with expansion members moving in the same direction) because they separate/collapse at a rate of 2 pitches per rotation and thus have twice the motion relative to the endplates.

In some embodiments, a size of the expansion member (e.g., screw) may be reduced to get the same force at a lower torque because passive rotation within one of the expansion members is more efficient. One may reduce the angle of the ramp or have a single ramp, but you would need considerably more travel to achieve the same height and would run into length limitations. Many embodiments described herein increase rotations not travel.

Forming the expansion mechanism from two elongated members as opposed to a single elongated member has several advantages. For example when retracting upper body 35 and lower body 40 from an engaged position to an unengaged position, torque applied to the expansion mechanism during retraction may lead to failure of the expansion mechanism when the expansion mechanism includes a single elongated member. When the expansion mechanism includes two elongated members, failure of the expansion mechanism when counter (retracting) torque is applied is inhibited.

In some embodiments, one or more of the expansion members may include a locking member 255. The locking member may be positionable in the second expansion member 55 such that the second elongated member is inhibited, during use, from removal from the opening in the second expansion member. The locking member may include a pin. The pin may be positioned in an opening in the second expansion member. In some embodiments, the locking member may engage a recess 260 in the second elongated member. The recess may circumscribe the circumference of the second elongated member such that the second elongated member does not have to be oriented in a particular direction relative to the second elongated member. In some embodiments, the locking member may be used in combination with the single elongated member (e.g., snap ring 215 as depicted in FIG. 2).

In some embodiments, first expansion member 50 includes a generally wedge-shaped body 155 having a superior camming surface 160, an inferior cam surface 165, a pair of superior fingers 170 and a pair of inferior fingers 175 (e.g., as depicted in FIG. 16). Significantly, superior camming surface 160 of first expansion member 50 extends parallel to camming surface 100 of upper body 35, and inferior camming surface 165 of first expansion member 50 extends parallel to camming surface 125 of lower body 40. In lordotic embodiments these surfaces may only be parallel in the open position. They are not parallel when closed. First expansion member 50 may include a threaded bore 180 extending there through. Threaded bore 180 is sized to be threadingly engaged by screw threads 147 on elongated shaft 135.

In some embodiments, second expansion member 55 includes a generally wedge-shaped body 185 having a superior camming surface 190, an inferior camming surface 195, a pair of superior fingers 200 and a pair of inferior fingers 205 (e.g., as depicted in FIGS. 16-17). Significantly, superior camming surface 190 of second expansion member 55 extends parallel to camming surface 105 of upper body 35, and inferior camming surface 195 of second expansion member 55 extends parallel to camming surface 130 of lower body 40. In lordotic embodiments these surfaces may only be parallel in the open position. They are not parallel when closed. Second expansion member 55 may include a smooth bore 210 extending there through. Smooth bore 210 may be sized to receive the portion of expansion mechanism 45 distal to annular shoulder 140.

Camming surfaces of the upper/lower bodies and the expansion members may be substantially flat as depicted in some of the attached FIGS. In some embodiments, at least some of the camming surfaces may be curved. Complementary camming surfaces may be complementarily shaped. Complementary camming surfaces may not be complementarily shaped.

In some embodiments, intervertebral implant 5 may be assembled so that expansion mechanism 45 extends through proximal opening 75 in cage 30 (without engaging proximal opening 75 in cage 30), and first expansion member 50 and second expansion member 55 are disposed on shaft 135 of expansion mechanism 45 within the hollow interior 65 of cage 30. More particularly, first expansion member 50 may be mounted on elongated shaft 135 of expansion mechanism 45 so that screw threads 147 are threadingly received in threaded bore 180 of first expansion member 50, and second expansion member 55 is mounted on elongated shaft 135 of expansion mechanism 45 so that second expansion member 55 is captured on elongated shaft 135 between annular shoulder 140 and a snap ring 215 secured in groove 145. At the same time, upper body 35 and lower body 40 may extend into hollow interior 65 of exterior body 30 so that (i) camming surface 100 of upper body 35 rides on camming surface 160 of first expansion member 50, (ii) camming surface 105 of upper body 35 rides on camming surface 190 of second expansion member 55, (iii) camming surface 125 of lower body 40 rides on camming surface 165 of first expansion member 50, and (iv) camming surface 130 of lower body 40 rides on camming surface 195 of second expansion member 55.

It will be appreciated that, as a result of the foregoing construction, the application of torque to expansion mechanism 45 in one direction (e.g., in a noncircular bore 150 in expansion mechanism 45) causes first expansion member 50 and second expansion member 55 to separate, whereby to move upper body 35 and lower body 40 apart and hence increase the height of intervertebral implant 5. It will be appreciated that, as a result of the foregoing construction, the application of torque to expansion mechanism 45 in the opposite direction causes first expansion member 50 and second expansion member 55 to draw together, whereby to move upper body 35 and lower body 40 together and hence decrease the height of intervertebral implant 5.

In some embodiments, the intervertebral implant 5 may include a curved cross-section. Straight designs are more commonly associated with PLIF (direct posterior placement in pairs), or lateral approaches (one longer device placed from the side of the spine). FIG. 21 is a schematic cross-sectional view of a curved expandable fusion device in an unexpanded state with a curved cross-section. FIG. 22 is a schematic cross-sectional view of a curved expandable fusion device in an expanded state with a curved cross-section. In some embodiments, portions of the implant may be curved or angled in order to accommodate the curved cross-section of the perimeter. In some embodiments, expansion members and the expansion mechanism may not require adjustments to assimilate into an implant with a curved perimeter. The distal end 235 of the expansion mechanism 45 a may engage a recess 240 in the second expansion member 55 as discussed herein and in the case of a curved implant the recess may adjusted to compensate for the varying angle of engagement of the distal end with the recess during expansion. In some embodiments, the distal end of the expansion mechanism may be curved in order to accommodate a curved perimeter.

The reason TLIF cages are typically curved is that the surgical technique would be to place them from a posterior-lateral approach, as much as 45 degrees off the midline, where they are tamped and rotated to the front of the vertebral body. A curved implant may facilitate insertion of the implant between adjacent vertebrae. An implant with a curved perimeter may better mimic and accommodate the existing perimeter of the average vertebra. FIG. 23 depicts a schematic view of a curved expandable fusion device 5 as the device is being inserted between two adjacent vertebrae. In some embodiments, the implant inserter may be curved. The expansion mechanism may have a flexible shaft to allow rotation within the curve. The relative advantages of an expandable feature may in fact be greater because it would significantly reduce the impaction required to maneuver the device into final position at the front of the spine.

In some embodiments, an implant system may include an implant insertion device 300. FIG. 18 shows a handle 215, a holder 220 and an engaging member 225 which may be used to manipulate and deploy intervertebral implant 5. More particularly, handle 215 includes two extensions 230 for positioning in seats 80 (e.g., as depicted in FIGS. 3-6) of intervertebral implant 5. Holder 220 may be positionable in handle 215 and threadingly engages the distal end of expansion mechanism 45, whereby to releasably secure intervertebral implant 5 to handle 215. Engaging member 225 may be positionable in holder 220 and into bore 150 in expansion mechanism 45, whereby to permit the user to turn expansion mechanism 45 and hence adjust the height of the intervertebral implant 5. Engaging member 225 may include engaging head 226 which engages bore 150. Engaging head 226 may include a complementary shape to bore 150 such that as the head turns the expansion member 45 turns.

In some embodiments, an implant system may include an implant insertion device 300. FIGS. 24-26 depict a schematic view showing insertion instruments 300 for use with an expandable fusion device. FIGS. 24-26 depict a handle 215, a holder 220 and an engaging member 225 which may be used to manipulate and deploy intervertebral implant 5. More particularly, handle 215 includes two extensions 230 for positioning in seats 80 (e.g., as depicted in FIGS. 24-25) of intervertebral implant 5. Engaging member 225 may be positionable in holder 220 and into bore 150 in expansion mechanism 45, whereby to permit the user to turn expansion mechanism 45 and hence adjust the height of the intervertebral implant 5. Engaging member 225 may include engaging head 226 which engages bore 150. Engaging head 226 may include a complementary shape to bore 150 such that as the head turns the expansion member 45 turns. In some embodiments, the insertion instrument 300 may include a grip 280 coupled to engaging member 225. In some embodiments, engaging member 225 may include a threaded proximal portion 285. The threaded portion 285 may function to assist in controlling longitudinal movement of the engaging member and therefore expansion of the implant.

In some embodiments, an insertion device may be disposable. FIGS. 27-28 depict a schematic view of a disposable expandable fusion implant insertion device 300. A disposable insertion device may be packaged with an implant. The insertion device may allow bone graft to be packed after insertion. The “disposable” option may allow the holder to act as an internal funnel which would make cleaning difficult, but a “durable version” remains an option. In some embodiments, engaging member 225 may be used to pack biological material into the implant through holder 220. In some embodiments, a separate packing instrument (not depicted) may be used to insert biological material.

FIGS. 32-36 depict a schematic view showing insertion instruments 300 for use with an expandable fusion device. FIGS. 32-36 depict a handle 215, a holder 220 and an engaging member 225 which may be used to manipulate and deploy intervertebral implant 5. More particularly, handle 215 includes two extensions 230 for positioning in seats 80 (e.g., as depicted in FIGS. 24-25) of intervertebral implant 5. In some embodiments, the extensions may be spring loaded (e.g., using springs, forming at least a portion of the extensions from an at least slightly flexible material, etc.) such that they are biased to be positioned such that they apply pressure to the seats of the implant during use. In some embodiments, a mechanism may be employed to engage/release the extensions from the implant.

The insertion instrument may include at least two holders 220 which couple to opposing sides (e.g., the inferior and superior surfaces of the implant) of the implant during use.

In some embodiments, the holders may be spring loaded (e.g., using springs, forming at least a portion of the holders from an at least slightly flexible material, etc.) such that they are biased to be positioned such that they apply pressure to the surfaces of the implant during use. In some embodiments, a mechanism may be employed to engage/release the holders from the implant. The holders may include a curved edge or lip which curve towards one another. The curved edge may engage an appropriately shaped portion of the proximal end of the implant.

Engaging member 225 may be positionable in handle 215 and into bore 150 in expansion mechanism 45, whereby to permit the user to turn expansion mechanism 45 and hence adjust the height of the intervertebral implant 5. Engaging member 225 may include engaging head 226 which engages bore 150. Engaging head 226 may include a complementary shape to bore 150 such that as the head turns the expansion member 45 turns. In some embodiments, the insertion instrument 300 may include a grip 280 coupled to engaging member 225.

In this patent, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) have been incorporated by reference. The text of such U.S. patents, U.S. patent applications, and other materials is, however, only incorporated by reference to the extent that no conflict exists between such text and the other statements and drawings set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference U.S. patents, U.S. patent applications, and other materials is specifically not incorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims. 

What is claimed is:
 1. An intervertebral implant for a human spine, comprising: an upper body comprising an inferior surface and a superior surface, wherein the superior surface of the upper body is configured to engage a first vertebra of the human spine; a lower body comprising a superior surface and an inferior surface, wherein the inferior surface of the lower body is configured to engage a second vertebra of the human spine; a first expansion member comprising at least a first angled portion positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body, wherein at least the first angled portion is oriented towards a first end of the intervertebral implant; a second expansion member comprising at least a second angled portion positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body, wherein at least the second angled portion is oriented towards a second end of the intervertebral implant, wherein at least the second angled portion is oriented in an opposing direction relative to at least the first angled portion; and an expansion mechanism conveys, during use, the first and second angled portions in opposing directions increasing a separation distance between the upper body and the lower body.
 2. The implant of claim 1, wherein the expansion mechanism comprises a threaded elongated member.
 3. The implant of claim 1, wherein the expansion mechanism comprises an elongated member comprising a proximally threaded portion, wherein the first expansion member comprises a threaded opening which the threaded portion of the elongated member engages, during use.
 4. The implant of claim 1, wherein the expansion mechanism comprises: a first elongated member comprising a proximally threaded portion, wherein the first expansion member comprises a threaded opening which the threaded portion of the first elongated member engages, during use; and a second elongated member positionable, during use, in an opening in the second expansion member; wherein a distal end of the first elongated member engages, during use, a proximal end of the second elongated member.
 5. The implant of claim 1, wherein the expansion mechanism comprises: a first elongated member comprising a proximally threaded portion, wherein the first expansion member comprises a threaded opening which the threaded portion of the first elongated member engages, during use; a second elongated member positionable, during use, in an opening in the second expansion member; wherein a distal end of the first elongated member engages, during use, a proximal end of the second elongated member such that the distal end of the first elongated member is positioned in the opening in the second expansion member; and a locking member which is positionable in the second expansion member such that the distal end of the first elongated member is inhibited, during use, from removal from the opening in the second expansion member.
 6. The implant of claim 1, wherein the expansion mechanism comprises: a first elongated member comprising a proximally threaded portion, wherein the first expansion member comprises a threaded opening which the threaded portion of the first elongated member engages, during use; and wherein a distal end of the first elongated member engages, during use, a proximal end of a recess in the second expansion member.
 7. The implant of claim 1, further comprising a cage forming a perimeter around the intervertebral implant in which at least portions of the upper body, the lower body, the first expansion member, the second expansion member, and the expansion mechanism are positioned, during use, in the cage.
 8. The implant of claim 1, further comprising a cage forming a perimeter around the intervertebral implant in which at least portions of the upper body, the lower body, the first expansion member, the second expansion member, and the expansion mechanism are positioned, during use, in the cage, wherein the cage comprises one or more openings along the perimeter to allow graft material to be positioned during use.
 9. The implant of claim 1, wherein the first angled portion comprises a wedge-shaped portion.
 10. The implant of claim 1, wherein the second angled portion comprises a wedge-shaped portion.
 11. The implant of claim 1, wherein the second end is positioned substantially opposite the first end.
 12. The implant of claim 1, wherein the first and second angled portions move, during use, towards opposing ends of the intervertebral implant.
 13. The implant of claim 1, wherein a lateral cross section of a perimeter of the intervertebral implant comprises a curved shape such that at least a first portion of the perimeter is substantially convex and at least a second portion of the perimeter is substantially concave, wherein the second portion is substantially opposite the first portion.
 14. The implant of claim 1, wherein the upper body and/or the lower body comprises an opening wherein graft material is positionable during use.
 15. The implant of claim 1, wherein the upper body and/or the lower body comprises an opening which increases in size as the first and second angled portions are conveyed in opposing directions.
 16. The implant of claim 1, wherein the superior surface of the upper body and/or the inferior surface of the lower body comprise teeth.
 17. The implant of claim 1, wherein the superior surface of the upper body and/or the inferior surface of the lower body comprise teeth which promote, during use, retention of the implant between the first vertebra and the second vertebra after insertion.
 18. A method for maintaining the spacing between two adjacent vertebral bodies, comprising: removing at least a portion of a disc between two vertebrae of the human spine to create a disc space between the two vertebrae; positioning an unexpanded intervertebral implant in the disc space between the two vertebrae, wherein the intervertebral implant comprises: an upper body comprising an inferior surface and a superior surface; a lower body comprising a superior surface and an inferior surface; a first expansion member comprising at least a first angled portion positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body, wherein at least the first angled portion is oriented towards a first end of the intervertebral implant; a second expansion member comprising at least a second angled portion positionable, during use, between the inferior surface of the upper body and the superior surface of the lower body, wherein at least the second angled portion is oriented towards a second end of the intervertebral implant, wherein at least the second angled portion is oriented in an opposing direction relative to at least the first angled portion; and an expansion mechanism; moving the first and second expansion members in opposing directions using the expansion member; and increasing a separation distance between the upper body and the lower body.
 19. The method of claim 18, further comprising engaging a first vertebra of the human spine using the superior surface of the upper body.
 20. The method of claim 18, further comprising engaging a second vertebra of the human spine using the inferior surface of the lower body. 